The Research On Laser Shock Peening And Characteristic Analysis Of Small Hole Components

Laser shock peening technology of small holes is a novel strengthening technology which is put forward because of the shortage of small hole traditional mechanical strengthening technology. Based on the existing research of the planar laser shock strengthening, the reflecting cone is introduced. Using transverse expansion effect of detonation wave in the reflecting cone end surface, laser shock peening technology of hole wall is theoretically researched. The dynamic process of laser shock peening of hole specimen, the comparison of different material components strengthening, the hole wall deformations of through-holes and blind ones, the residual stress field and micro structure of hole wall surface are studied by method of numerical simulation, providing reference for practical application of laser shock peening technology of small holes. The main work can be concluded as follows:First, based on the laser induced shock wave theory and the formation mechanism of residual stress field, the advantages of confined model are analyzed, the calculation method of shock wave pressure is investigated, the valuation formulas of the peak pressure of laser shock wave are derived, the dynamic response under shock wave and the laser induced residual stress field are analyzed.Secondly, using finite element software ANSYS/LS-DYNA, the dynamic processes of laser shock peening of LY12 CZ aluminum alloy and copper hole specimens are numerical simulated, and the dynamic response characteristics are investigated. Then the dynamic simulation results are imported into ANSYS for static analysis. The distribution characteristics of the stable residual stress generated by laser peening are studied. And the effects of impact times and different materials on strengthening results are investigated by the above procedures.Finally, using high energy laser, the laser shock peening experiments of LY12 CZ aluminum alloy and copper specimens are carried out. The surface morphology of hole wall treated by laser shock peening is observed by 3D metallographic microscope DSX510,and the hole wall radial deformation at the top of the reflecting cone is analyzed; using X-ray diffraction method, the laser induced residual stress of the hole wall is measured,and the result shows that the experimental result is consistent with the simulation one; the surface microstructure is observed by SEM and optical microscope, and the surface material grain refinement of the shocked area and the dislocation structure of hole wall strengthening layer are analyzed. The mechanism of laser shock peening in promoting behaviors of components is explained from the microscopic angle.